Experimental Study of Biodegradation of Ethanol and Toluene Vapors

than 4.0 mg/L at all dilution rates up to 0.25 h -1 , i.e. oxygen is not a rate-limiting factor
for these operations.
Figure 5-15b shows biomass (X), benzyl alcohol (C b ), ammonia (C n ) and
dissolved oxygen (DO) at a benzyl alcohol feed concentration of 1.2 g/L. When the
dilution rate is higher than 0.27 h -1 , the cells are washed out (X=0). Since no microbial
consumption happens, the substrate concentration is the same as the feed (C b = C b0 ).
This figure also reveals that the DO level is above 0.75 mg/L for all dilution rates up to
0.27h -1 , which is higher than the critical oxygen value. Thus, the system can be
maintained at steady state for all dilution rates up to 0.27h -1 at feed concentration of
1.2g/L.
Biomass and benzyl
alcohol concentrations
(g/L)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
DO
X
C b
0
0 0.1 0.2 0.3
Dilution rates, h -1
7
6
5
4
3
2
1
Dissolved oxygen (mg/L)
Figure 5-15(a). Prediction of continuous removal of benzyl alcohol (C b0 = 0.66 g/L)
137